The search portal of the Performing Arts Information Service offers cross-institutional research in library catalogs, archive databases, and other information sources with a specific focus on the performing arts. Here, you can also search some of the holdings of the dance archives. 
 

https://www.performing-arts.eu/

Europeana offers digital access to Europe's cultural heritage to anyone with a personal or professional interest in it, as well as to teachers and researchers.

https://www.europeana.eu/de 

The German Digital Library provides access to Germany's digitized cultural and scientific heritage.

https://www.deutsche-digitale-bibliothek.de/

In addition, the individual holdings of the dance archives can be searched in separate databases or online catalogs:
 

At  www.tanz-digital.de , materials on specific topics can be viewed as a showcase of the dance archives.